1. Field of Invention
The invention relates to an arrangement for illuminating the adjusting knob of an input unit by means of transmitted light, the input unit having a rotary switch which is fastened on a dividing wall and the setting stem of which, carrying the adjusting knob, reaches through to the opposite side of the dividing wall, and at least one light source being provided, located on the rotary switch side.
2. Description of the Prior Art
The transmitted-light illumination of the adjusting knobs of input units which are to be flange-mounted on a dividing wall, for example on a dashboard, is problematical to the extent that, by contrast with a commercially available, ready-to-install device, the input unit, adjusting knob and light-guiding means have to be assembled directly at the dividing wall. At the same time, because of the dominance of illumination of this type at night-time, the uniform illumination of the adjusting knob has to meet high requirements, whether the latter is intended to light up in its entirety or only in an outer region, or markings or scales of the adjusting knob are to be made distinguishable. On the other hand, in particular in a case where the setting unit [sic] is used in a motor vehicle, the conditions of mass production and mass assembly must be taken into account for the illumination of the adjusting knob.
It was consequently an object of the present invention to illuminate by means of transmitted light the adjusting knob of an input unit assigned in the generic way to a dividing wall, with as little outlay as possible.
The way in which this object is achieved is characterized in that a light guide is provided, in that on the light guide there is formed a light-exiting face corresponding to the region of the adjusting knob to be illuminated, in that the light guide is fastened on the dividing wall on the adjusting knob side and in that the light guide reaches through the dividing wall to the light source. A preferred embodiment provides that the rotary switch is assigned a printed-circuit board, that contacted light-emitting diodes serve as the light source on the printed-circuit board and that the light guide is designed as a conical ring with light-guiding continuations formed on in the axial direction and assigned to the light-emitting diodes.
It can be seen as the decisive advantage offered by the invention that only a single light-guiding component, produced by the injection-molding process, is required for the light guidance between the light source and the adjusting knob and that homogeneous illumination of the adjusting knob, in the case of the exemplary embodiment of a row of illuminated points provided peripherally around the adjusting knob and visually representing, for example, the switching steps of the rotary switch, can be realized with just three light-emitting diodes. It must also be emphasized that the light guide according to the invention can be fastened in a simple way, that is to say indirectly when the input unit is fastened. In the case of the particularly advantageous coaxial arrangement, according to the exemplary embodiment, the light guide represents as it were a shim, the flange surfaces not being optically relevant. In this connection, it should be emphasized that the light guidance provided within the light guide has only a few optically effective faces, that is to say necessitates faces of a high surface quality. Furthermore, the light guide in interaction with the through-opening which is located in the dividing wall and is provided with indentations, or in interaction with bores which are assigned to the through-opening and are provided for the reaching through of the light-guide channels or the light-guiding continuations of the light guide, represents a twist-preventing means for the input unit if the rotary switch is assigned a housing and the fastening of the input unit takes place by means of a threaded lug formed on the housing. On account of the twist-preventing function, the fastening moment can be reduced and, in this way, fastening that does not cause any damage and is resistant to creep can be achieved for the plastic housing receiving the input unit.
It is of fundamental significance that this makes it possible in a simple way for the invention to guide a light serving for the transmitted-light illumination of an adjusting knob, or else the illumination of a scale formed on an adjusting knob, from one side of a dividing wall, for example a dashboard, on which the input unit concerned is flange-mounted, to the other side of the dividing wall, on which the adjusting knob is located.
For the sake of completeness, it should also be pointed out that the scale of a rotary switch with a limited rotating angle can also be illuminated in the same way by means of transmitted light, it possibly being necessary for such sectoral illumination that only two light-emitting diodes are provided or only one light-emitting diode is provided as the light source. Moreover, a wide variety of rings of light or designs of scales, for example also rows of symbols, can be illuminated in the way according to the invention by means of transmitted light. The same applies to various configurations of adjusting knobs. Furthermore, as represented in the exemplary embodiment, an arrangement of a light guide and adjusting knob may also be set up in such a way that the adjusting knob reaches around the light guide and in this way cuts out scattered light, or the adjusting knob is arranged at a certain distance from the light guide and consequently a halo of light is produced on the dividing wall as a result of the emerging scattered light.
The light distribution which can be achieved with the arrangement according to the invention, that is to say with a minimum of light-emitting diodes, and the uniform illumination of the adjusting knob or of the ring of illuminated points provided for illuminating the adjusting knob is [sic] caused to a great extent by the deflecting faces which are formed at the depressions of the light guide and are assigned to the light-guiding continuations. In this arrangement, each deflecting face guides the received light into a portion of the ring that is asymmetrical with respect to the annular form of the light guide, whereby an overlapping of the streams of light of two neighboring deflecting faces occurs. This additionally achieves the advantage of compensating for differences in brightness between the light-emitting diodes used. The sector-shaped regions of low light intensity, existing in theory symmetrically in relation to the radial planes of intersection of the deflecting faces or parting planes of the depressions, are, as tests show, sufficiently flooded with light on account of the arrangement and formation of the deflecting faces.